The Montgomery County temperature reading on his iPhone: minus-1. It was the coldest day in the District since 1996, with a low of 6 degrees. Dulles Airport broke its record low for the date, dipping to 1 degree.

Brinkhoff bundled up in proper winter wear (coat, hat, etc.) before setting off for his investment newsletter job in Gaithersburg.

As the polar vortex put the Washington area into a deep freeze, the weather seemed to divide people into two categories: Those who were undaunted by the extreme cold and everybody else — the shivering masses who braced for the weather rather than attacking it with bravado.

Bravado — brrrrrrrrr-vado? — was New England native Alex Shabo, 24, who wore shorts on her morning run. It was the construction worker who ventured outside the massive CityCenterDC project for a smoke, wearing a sweatshirt sans jacket. It was Michael Forster, a 30-year-old lawyer who walked to his Logan Circle gym in a T-shirt.

“It’s just right next door, and I didn’t want to have to carry a coat and stuff,” he said. “I definitely got looks.”

Forster grew up in Troy, Mich., where single-digit temperatures are a common kind of cold. “I think it’s a lot mental and what you’re prepared for,” he said.

How people cope with extreme weather usually depends on their experiences, especially their recent exposure to cold and heat, according to researchers.

“We react to weather in relative rather than absolute fashion,” said Laurence S. Kalkstein, a professor in the Department of Public Health Sciences at the University of Miami. “The uncommon is what bothers us.”

Washington is not Fargo, N.D., so most of the region’s inhabitants confronted the vortex with caution, staying home or piling on so many layers that the region appeared to be under attack by an army of Michelin Men.

One of them, Norman James, was armed with a leaf blower. He was outside Industrial Bank in the Northwest Washington neighborhood of Petworth, trying to tidy up a stretch of sidewalk, because . . . why exactly?

Pacing along Georgia Avenue, the part-time landscaper wore a brown jacket. And a blue jacket. And a gray jacket. Plus long johns and double-sweatpants, among other layers.

His wardrobe strategy: “Three of every damn thing.” Even so, his runny nose was icing up his gray mustache.

This was cursing weather. Outburst weather. Guttural-utterance weather, as in, “wuuuooough!” when a gust swept into his hood.

“Cold as I don’t know what,” said James, who had been leaf-blowing for 20 minutes, and was going to keep working for another 20 before calling it a day and going to a movie. “I ain’t going to be out here in this damn cold,” he declared.

Wind chills were as low as minus-15 across the region.

It was so cold that the two Secret Service cars idling in front of the White House had icicles hanging off their exhaust-spewing tailpipes. It was so cold that the ink in a reporter’s pen froze. It was so cold that it reminded Julie Wolf of winter in Minnesota.

“In Minneapolis, these temperatures would be regular,” said Wolf, a climate researcher in College Park, Md. She once lived in Minneapolis, where the high Tuesday was lower than Washington’s low. But she’s been here now for more than a decade. She doesn’t do bitter cold anymore.

So she drove to work Tuesday rather than riding her bicycle. Score one for the polar vortex.

“I don’t like to be defeated by the weather,” she said. “It does make me feel like a loser. “

Really, though, she’s just a local. People adapt to new climates when they move, said Kalkstein, the Miami biometeorologist. Some researchers think it takes just a matter of weeks to become acclimated.

The professor himself grew up in New York and lived in colder-climate East Coast states until moving to the southwest tip of Florida in 2002. Highs have been in the 80s for most of this winter, he said.

“I’m not adapted to the cold weather anymore. It got down to 51 here this morning, and I’m freezing! I’m sitting here in a sweatshirt and jeans and don’t want to go outside.”

He especially does not want to visit his son, who lives near West Point, N.Y., where it was barely above zero Tuesday morning.

“He wants us to come and babysit the grandkids,” Kalkstein said. “But the thought of going up there is literally chilling me to the bone. . . . I have about the thinnest blood now. I don’t say that in a physical sense. It’s in the mental sense. It’s what you get used to.”

As the cold-weather sirens were sounded over the weekend, fear of the unknown gripped Washington and other temperate-winter cities in the polar vortex’s path.

Of course it did, said Shmuel Lissek, founding director of the ANGST Laboratory at the University of Minnesota.

“We tend to be more afraid of things that are unknown to us because it’s hard for us to accurately calculate how bad they’re going to be,” he said.

Nothing wrong with acting on that angst; it’s in our genetic nature, Lissek said. “We are the inheritors of an ancestry that erred on the side of caution.”

“I was scared of going out,” she said. “I thought of being frostbitten. We are not used to these temperatures. It makes me anxious. I think: ‘What will I wear? How can I protect myself?’ Then you think if the car breaks down because it is so cold, what will you do? You worry about your pipes freezing in your house. Cold is more scary than heat. In the heat, you can sweat. You can find some shade or go into a building, but when you are cold, you are cold.”

To overcome the fear of cold, Groover took a warm bath hours before she went out. She guzzled green tea. Then, she layered up: heavy shoes, turtleneck, hat, scarf — the works.

J. Freedom du Lac is the editor of The Post's general assignment news desk. He was previously a Local enterprise reporter and, before that, the paper’s pop music critic.

Donna St. George writes about education, with an emphasis on Montgomery County schools.

Mike Laris came to Post by way of Los Angeles and Beijing. He’s written about the world’s greatest holstein bull, earth’s biggest pork producer, home builders, the homeless, steel workers and Italian tumors.

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